Repeated head trauma experienced by some football players, wrestlers, boxers and other athletes may put them at risk for chronic traumatic encephalopathy, a progressive brain disease with Alzheimer's-like symptoms, say researchers at Boston University's School of Medicine.

Through autopsies, researchers at the school identified the disease in the brains of former NFL lineman Tom McHale, who died last year at age 45, as well that of an 18-year-old high school football player, says Robert Stern, PhD, a BU neuropsychologist and co-director of the university's Center for the Study of Traumatic Encephalopathy.

Preliminary research suggests that repeated head trauma cause the toxic protein tau to build up in the brain, leading to neurofibrillary tangles and the death of neurons, causing such symptoms as cognitive impairment, depression, erratic behavior and emotional instability. The disorder is untreatable and gets worse over time, leading to dementia, says Stern.

Researchers don't know why some athletes develop the disorder while others stay healthy upon retirement, Stern notes. However, McHale was the latest of six former NFL players age 25 to 50 whose brains have shown evidence of a disorder that's virtually unheard of among people who don't play contact sports, he says. The researchers' discovery of the beginning stages of the condition in a high school football player may also give parents pause, he notes.

"Parents, coaches, trainers and athletes all need to be aware of the potential consequences of concussion and other head trauma in sports and the need to fully recover before returning to play," Stern notes.